// 直接把一个数字类型的数组转换成字符串类型
var arr = [1, 2, 3, 4, 5, 6, 7, 8, 9];
let brr = arr.map(String)
// console.log(arr);
// console.log(brr);

var a = ['1', '2', '3', '4', '5', '6', '7', '8', '9']
let b = a.map(Number)
console.log(b);

